The present invention relates to an arrangement for treating a patient by means of proton therapy according to the pre-characterizing clause of claim 1 as well as uses of said arrangement.
Although proton radiation therapy is advantageous particularly for the irradiation of tumors, it is still only used to a very limited extent because of high costs and the large amount of space required for such installations.
Proton therapy is nowadays preferably applied with the aid of a rotating beam delivery system, referred to as the gantry.
The system is mounted on a rotating structure and can therefore be rotated around the patient table. This configuration enables the beam to be applied sequentially to the patient (lying in his immobilization device on the patient table) from several irradiation directions.
For the treatment of deep-seated tumors using proton therapy, the required energy of the proton beam is between 70 and 250 MeV. Because of the considerable beam rigidity, the gantry requires a large amount of space (using normal magnets, the minimum deflection radius which can be applied to the beam is at least 1.3 m) and is correspondingly heavy. Gantries for photon therapy are typically 10 m long, have a diameter of 4 to 12 m and weigh up to a hundred tonnes.
A modern gantry system is expected to enable the patient table also to be rotated about the vertical axis in the horizontal plane (in addition to the axial rotation of the gantry). The aim of this is to ensure that virtually all irradiation directions to the patient lying on the table can be selected from the system (ideally a 4π solid angle). The rotation of the patient table and gantry are therefore equally justified in functional terms. The new concept of this work is to limit the rotation of the gantry to +/−90° and to utilize the full 360° rotation capability of the table for this purpose (like the latitudinal and longitudinal division of world geography). For historical reasons, this relationship has been implemented the other way round in all previous systems, i.e. rotation of the gantry through 360° and of the table only through 180° maximum.
Today's commercially available systems are based on the concept that the gantry can be rotated completely through 360° about the longitudinal beam axis. The principle of a conventional system of this kind will now be described schematically and in detail with reference to FIG. 1.
The Paul Scherrer Institute has already made a significant contribution to the development of proton therapy. PSI's Gantry 1 is the world's second oldest photon gantry after Loma Linda in California. In operation since 1996, it is still the only gantry employing dynamic beam-scanning. It remains the gantry with the smallest diameter anywhere (4 m). A number of features derived from the PSI system have already been used in modified form for industrial patents. Such systems are described, for example, in the two European patents EP 0 911 964 and EP 0 864 337.
Experience with the present system has shown us the importance of good accessibility to the patient table in each radiation phase.
International patent application WO 01/00276 on this subject from the year 2000 (priority 1999) describes a device for performing proton therapy wherein the proton beam guiding and controlling device is implemented so that it can pivot or rotate only through a maximum angle of 270°, so that, as required, good accessibility to the patient table is ensured in each phase of radiation. WO 01/00276 will not be described in detail here, but a proton radiation arrangement similar to WO 01/00276 will be described schematically in further detail with reference to FIG. 2.
Although the requirement for accessibility to the patient table is met in the arrangement according to WO 01/00276, the requirement for dimensional reduction and simplification of the gantry remains. One object of the present invention is therefore to propose a different arrangement for performing proton therapy which, on the one hand, ensures continuous accessibility to the patient table without penalties in terms of functionality and, on the other, allows further simplification and increased accuracy in performing proton therapy, as well as in particular a further reduction in the dimensions of gantry components and of the gantry itself.
This object is achieved according to the invention primarily by means of an arrangement as set forth in claim 1.